The invention concerns devices for optically determining the position of objects.
Such devices are known from DE 200 00 868 U1 and used, for example, to detect whether a protective or safety door, provided, for example, to safeguard a hazardous machine or plant, is open or closed. The position detection device is part of a safety mechanism of the type which includes an electrical interlock with the controls for a machine, so that, for example, when the safety door is open, a dangerous condition at the machine can be eliminated or prevented by an appropriate shut-off procedure. The areas of application of the position detection device are described at length in DE 200 00 868 U1, and express reference is made here to the disclosure of DE 200 00 868 U1.
The known position detection device has the drawback that it employs an optical system that is based on the triangulation principle. It requires close tolerances, which increases installation and adjustment costs and may also lead to malfunctions, such as an early shut-off, or a failure to turn off the machine. It would therefore be desirable to have the ability to readily select the tolerances so that they suit the encountered application and safety requirements.